Do Now: 1. Take out homework 2. HSA practice:

Animal cells contain an organelle that helps release energy. A

diagram of this organelle is shown.

What is the organelle described?

A. chloroplast

B. mitochondrion

C. nucleus

D. ribosome

Natural Selection in Action

This field of corn has lots of weeds in it. Weeds take nutrients from the soil the corn plant needs.

RoundUp Ready Corn

• RoundUp is a chemical that kills plants.

• 90% of the corn grown in the US is genetically modified to have resistance to RoundUp.

• Since the corn is resistant, farmers can spray roundup and kill everything but the corn

It worked for a while…

But there was VARIATION in the weeds

• A tiny % of the weeds were naturally resistant to the RoundUp and survived…

ResistantWeed

Now, that weed had offspring… and they had offspring… etc. etc.

• Since resistant weeds are the only ones that survive and reproduce, they are now far more common in corn fields.

ResistantWeed

ResistantWeed

ResistantWeed

ResistantWeed

ResistantWeed

That’s Evolution!

• An abiotic factor in the environment (RoundUp) has selected a trait in the population of weeds – RoundUp resistance.

• The weeds have adapted to their environment.

• Adaptation: 1. the process by which a population becomes better suited in its habitat. 2. A feature that is important to an organism’s survival

Adaptations

• What adaptations do these organisms have that help them survive?– Humans– Bears– Fish– Ducks

Homology = Similarity

• Homologous structures are alike in basic structure and origin (like flippers and wings)

• Genetic homology or DNA homology measures how similar DNA sequences are.

DNA Homology

Homology = Relatedness

• Organisms which share homologous structures or DNA are related to each other.

• The more homology there is between two organisms, the more closely related they are.

Organisms are Classified by their Similarities and Differences

• Phylogeny is how groups of organisms are related to each other

• A cladogram or phylogenetic tree is a diagram that shows these relationships

Cladogram

Making a Cladogram

• We will be making a cladogram that shows how 7 different organisms are related to one another based on their characteristics

The animals

The CharacteristicsCanine Teeth Paired Appendages

Mammary Glands

Amnion

VertebralColumn

Paired Legs

Foramen Magnum